A Pressurized Water Reactor is a type nuclear power reactor in which the heat of fission affects water in a primary loop, which is piped to a heat exchanger that generates steam in a secondary loop that drives the turbine; water in the primary but not the secondary loop is radioactive. While it is larger and more mechanically complex than a Boiling Water Reactor, it is easier to maintain because the turbines and associated equipment do not become radioactive.